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Discussion Starter · #1 ·
Ok so I have been having this problem on my 2008 Mustang GT.. I have been having a weird idle.. rpms drop intermittently, sounds like a misfire from my exhaust (have Cervinis side exit exhaust, so I can hear it relly well) not a steady sound like before, intermittently the sound changes, and my engine feels out of balance.. I can put my hands on the engine and fell like it intermittently jerking..

I have changed the fuel filter, fuel injectors, spark plugs, oil and filter, maf sensor and 2 of the coil on plugs..

Only mods I have is full Cervinis body kit with side exit exhaust, o/r h-pipe, JLT cai with 91 octane bama tune
Today i hooked up my timing light to the wires that go into the coil on plugs to check for spark and all seemed to fire fine cept for 2 seemed to have slight pause bout every 7 or 8 seconds and one just intermittently fires the light.. Have tried to move the coil on plugs around and still does the same thing.. any thoughts? Am not getting any codes and sometimes if stopping at a light it the rpms will drop down and then the computer will pick it back up, does this while sitting in neutral and barely revving the engine.. What would cause the computer to not be firing the coils right?
 

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Discussion Starter · #4 ·
I have taken the throttle body off and gave it a deep cleaning.. still the same thing.. I ordered some new accel cop's today so hopefully that will maybe fix the issue.. Like I said I am worried about the intermittent flashing of the timing light, not just on one but like 2 or 3.. Sounds like I can hear the exhaust tone change when the light pauses. Weird that I dont get any cel.. guess it could be that the spark is really weak

Also seems like maybe my battery voltage is slowly getting low.. Tested it not that long ago and it was bout 14 with everything on and the last 2 tests have shown lower, this last one being between 12.9 and 13.2 volts
 

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Stock COP's are remarkably reliable. Most folks have reported poor results with aftermarket COP's...the stockers are good beyond 1,000 RWHP.

What plugs are you using? Perhaps try some Brisk Silver racing. Did you check your plug gap? Try .035 if blown... .040 is fine if not.

Did you insure the COP springs are clean and use some dilectric grease upon assembly?

Fresh fuel? Water in gas? Just thinking out loud...maybe try some Seafoam?

Make sure the throttle body and inlet elbow (if blown) are all tightened down, check air filter and intake for leaks, etc.

Lastly (you are on this track) check battery and alternator.
 

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Black Beauty. I was showing a p0300 random misfire fo 2 years finally changed plugs and coils had Brenspeed dyno the car it never returned. People where telling me it was the cams some would even say it was the ud pullys. but once I changed the coils it stopped. Good luck keep us posted.
 

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Discussion Starter · #8 ·
Hey guys, thanx for all the great responses.. I will try and answer them all.. DiMora, I bought the oem plugs (motorcraft sp509) and the gap is preset and the ford guy told me not to try and mess with them cause they are the fine wire ones and it will mess them up. It says they come at .41 which is the spec but when I checked them my gap says they are .45, which I checked the stock ones too that I took out and same thing .45.. I dont know maybe my gapper is wrong lol.. I have not tried to take the the cop springs out and clean them yet, will try tomorrow even though they seem pretty clean. I have look for air leaks and cant find any.. and I have tried seafoam in the intake and crankcase (changed the oil right after). I dont know what else to do.. I have changed all of the things listed above to no solution.. Only thing left I think is cop's, timing and compression check..

Speaking of that, let me give a brief recent history.. Now I do remember that it seemed like it started doing this right around the time (not that long ago) that I got an oil leak at the front main seal. It was under full warranty so I took it to Ford and they replaced the seal, front cover gasket, valve cover gasket and oil pan gasket. For one cause you have to take all of that off to take the front cover off, which is one reason I am avoiding checking the timing to see if maybe it just time or somnething.. lots of work.

You what is really sad is i got tired of spending the money and throwing parts at it, I am in the Army so that says it all bout finances lol, so i took it to Ford and the guy called me back bout an hour later and said he cant diagnose it cause it had the cai and aftermarket exhaust, his people are not used to seeing that. I was like really, you are a ford certified mechanic.. anyways so then i took it to 2 other shops and they said it is too new and i should just take it to Ford, so I took it to a speed shop and the guy said it was running a little rich (ltft's were -8) and the only thing he could do was put it on the dyno and see what he could do. Didnt have the money at the time.. Sucks cause the car used to run so smooth and fast and now it kinda hesitates on takeoff, idle feels rough and vibrates and shakes the car, and when driving feels like the car weighs like 10000 pounds, really sluggish..
If anyone knows how to read a data logger I can tell you anything you wanna know or I can post my datalogger readings. I just dont really know how to interpret it. I have a sct xcal 3.
 

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If you want to rule out the Bama tune, throw the stock CAI and stock tune back in and see if it still happens?

If you have datalogs, let the Bama guys know what's going on - explain to them the things that you've replaced and then shoot them the datalogs. They can probably easily diagnose what's going on. They're available at the Bama direct number and hours in my signature. Good people, let us know what they say!

Also, how many miles do you have on your car?

Chris
 

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Discussion Starter · #10 ·
Yeah never thought of that.. i will try and call them tomorrow. You from American Muscle.com? That is where I just ordered my Accel cop's from yesterday. I love that sight. Pretty much got all of my stuff from there to include the tuner and cai..
 

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Discussion Starter · #13 ·
Ok update: Bama said they didnt have enough info to diagnose it so... and I got my new accel coil on plugs and it runs stronger but problem is still there.. /sigh at my wits end..
 
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